Adding Noise and Predistortions, and Impairing the Signal
R&S
®
SMBV100B
256User Manual 1178.4460.02 ─ 03
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Scalable lowpass filters are used to produce a noise level with both a broad
dynamic range and a broad bandwidth range.
AWGN modes
The AWGN generator generates signal in one of the following different modes:
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"Additive Noise": the generated noise signal superimposes the interference-free
useful signal
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"Noise Only": a pure noise signal is generated and modulated to the carrier; the
connection to the baseband is interrupted.
Figure 4-1: Representation of an AWGN > Mode > Noise Only in the block diagram
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"CW Interferer": a sinusoidal signal with an adjustable frequency offset and car-
rier-to-interferer (C/I) power ratio is added to the baseband signal.
Signal and noise parameters
The Figure 4-2 illustrates the relation between the signal and noise parameters.
Figure 4-2: Graphical representation of the relation between system bandwidth and noise bandwidth
(Minimum Noise/System BW = 2)
System BW* = Occupied BW
The system bandwidth is a measure for the transmitted RF bandwidth. The selected
value is usually the occupied bandwidth and is therefore a value greater than the pure
signal bandwidth.
In the most test cases, the signal and the noise power are not defined directly but with
the target signal-to-noise ratio (SNR) or carrier/noise ratio.
The carrier power is a measure for the signal without the noise distribution. This indi-
cation corresponds to the "Level" value in the "Status bar" (see Figure 4-3).
Adding Noise to the Signal
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